In Patent Literature 1 (JP-A-2002-67165), disclosed is a method for providing a concave part on a laser irradiation part on a transmitting resin side, shortening a transmission distance, and making welding effectively as a method for making laser welding of a housing for storing measurement devices and a cover for covering them in a measuring instrument such as a thermal type flow meter. Further, in Patent Literature 2 (JP-A-2009-056722), disclosed is a method for providing an opening on a transmitting resin side and determining welding in a state in which a welded part is evaginated as a method for inspecting a laser welded part.